Single packer oil production method



March 19, 1957 R. SPEAROW SINGLE PACKER on. PRODUCTION METHOD 2Sheets-Sheet l Filed June 28, 1954 March 19, 1957 R. SPEAROW SINGLEPACKER on. PRODUCTION METHOD 2 Sheets-Sheet 2 Filed June 28, 1954 I I II I I f I l f fl 7/2 $1 ZZMWY l I I V I I I! I lvvflflllllllll If? lINVENTOR. Pa/ph' Spear-ow United States @atenr SlNGLE PACER 031. PP, DUJ'HQN METHGD Ralph Spearow, Paola, K

Application June 28, 1954, Serial No. 431,523.

9 Claims. (ill. 166- 42) vious applications: Serial No. 262,568, filedDecember 20, 151, now Patent No. 2,725,166, and entitled Oil Production;Serial No. 360,645, filed lune 10, 1953,

entitled Multiple Horizon C'il Production Method, and Serial No.363,804, flled June 24, 1953, and entitled Movable Packer Oil ProductionMethod. Serial No. 262,568 is in turn a continuation in part of myearlier application, Serial No. 750,396, filed May 26, 1947, and

issued on April 22, 1952, as Patent No. 2,593,497.

My previous applications set forth various means,

methods, and apparatus for accomplishing vertical pressurization andproduction of oil from oil well horizons.

The distinctive feature of my vertical gaseous pressurization oilproduction methods, as set forth in my previous applications and in thepresent application, .is that gaseous pressure is applied to the topportions of the oil horizons. and oil isproduced from the lower portionsof said horizons, the oil within the horizon being driven verticallydownward by the pressurization. The pressure medium in the form of airor gas is supplied to the top portion ofthe oil horizon from anysuitable convenient source. This pressure medium is introduced atpressures in excess of the rock pressure in the oil sand, but controlledto enter the oil sand at a rate which will cause gradual migration ofthe fluid oil from the upper region to the bottom of the sand. if air isused, since it-does not blend with the gas and oil in the formation aswell as does natural gas, it will form in a pressure pocket surroundingthe wellbore (input well bore) extending outwardly and'downwardlytherefrom causing the liquids in the sand. to move ahead of it in alldirections. This movement of fluids in the oil producing formatiom'thusbegun, causes a general movement in the. vicinity of the welldownwardly, the pressure effect diminishing at increased radialdistances from the axis from the input well. As pressures are increased,movement of the fluids in the formation will likewise increase, bothwith respect to the rapidity of movement and over all areas influenced.Patent No; 2,593,497 shows a combined pressurization and production wellhaving a pressure input area at the top portion of the oil horizon and aproduction area at the lower portion of the oil horizon, employing acasing extending through the oil horizon, said casing sealed to the wellwall through the oil horizon and perforated in extending through the oilhorizon, said casing sealed to the well wall through the oil horizon andperforated at its .lower portion: to form :the production area.

ice

Serial No. 360,645 illustrates, among other structures, separatepressurization and production wells, the production well having a tubingextending through the oil sand, said tubing gravel packed in its bottomportion and sealed to the well wall from the top of the gravel packedarea to a level above the top of the oil horizon.

Serial No. 363,804 illustrates, among other structures, separatepressurization and production wells, the production well having a tubingextending into the oil horizon, the tubing packed off below thepressurization medium sand fluid interface, said packer beingsuccessively moved downwardly as the pressurization medium-sand fluidinterface moves downwardly during the oil horizon pres- V surizationprocess.

Patent No. 2,593,497 and Serial No. 262,568 illustrate methods andapparatus which, under certain circumstances, cause difliculty in thevertical pressurization oil production process. Both of theseapplications show production casings extending through the oil horizonand sealed thereto, the casings and their surrounding seals beingperforated to permit pressurization of. the upper portion of the horizonand/ or production of oil from the lower portion of the horizon. One ofthe main problems in the perforation or shooting of the casing and itssurrounding aunular sealing column, trouble is. often encountered,especially if the proper type of sealing-material is not employed, inchanneling of the sealing column under the impact of the shootingprocess.

In application Serial No. 363,804, in the apparatus which employs asealed casing as in 262,568, the same sealing and channelingdifficulties may be encountered.

Additionally, where a single packer is employed in an oil horizonpositioned on a tubing, the packer sealing said tubing to the well boreface, there is often dificulty in by-passing by fluid or pressure mediumof the seal between the packer and the well wall face, particularlyshould the vertical permeability be low inany. particular section of thewell bore face. Additionally, often ,a packer of large cross-sectionalarea must be employed and it is sometimes difilcult to successfully sealsuch a packer across its entire face to the well wall. Furthermore, inthe latter case, it is difficult and tedious to keep moving a the packersetting downwardly in the hole bore as the pressurization medium-sandfluid interface .migrates downwardly in the pressurization process.

in the application Serial No. 360,645, complete sealing of the entireoil horizon well bore face is shown save the small oil production areaat the bottom of the oil sand. This complete sealing process is oftentoo expensive to be desirable. Additionally, Serial No. 360,645 islimited to the situation wherein the Well bore hasa shot cavern in thevicinity of the oil horizon and gravel packing is employed.

Therefore, an object of the present invention .is. to provide apparatuswhich effectively seals the bore hole of a combinedpressurization-production well or production well from thepressurization medium-sand fluid interface to the oil production zone ina vertical pressuriza tion oil production method without (a) running acasing to the bottom of the bore hole of the well, sealing the casingfrom the bottom of the bore hole toa level above the oil horizon, andperforating thecasing and its surrounding seal, or (b) sealing a tubingextending to the lower portion of the oil horizon from the vicinity ofthe bottom of the horizon to a level above the oil horizon.

3 A further object of the present invention is to provide a method ofproducing oil from oil wells by a vertical pressurization method,employing an open well bore below the top of the sand, a tubingextending into the oil horizon with a single packer sealing said tubingto the well wall face, wherein it is not necessary to keep moving thepacker downwardly as the pressurization mediumsand fluid interface dropsdownwardly during the oil pressurization process.

Another object of the present invention is to provide a method ofproducing oil from oil wells by a vertical pressurization'methodemploying an open well bore below the top of the oil horizon, a tubingpositioned in the oil sand having a single packer sealingsaid tubing tothe well wall face wherein it is not necessary to keep the packer movingdownwardly as the pressurization "medium-sand fluid interface recedesdownwardly in the horizon and wherein the oil pressurization areaprogressively increases as the interface lowers within the horizon.. V

Another object of the present invention is to'provide a method ofproducing oil from oil wells by separate pressurization and productionwells wherein the production well bore hole does not have a shot caverntherein and there is no need for gravel packing, wherein the lowerportion of the oil horizon is merely packed off and an annular column ofsealing substance against the well wall face is established above thepacker.

Other and further objects will appear in the course of the followingdescription. 7 In the accompanving drawings which form a part of theinstant specification and are to be read in conjunction therewith, andin which like reference numerals indicate like parts in the variousviews, there is shown combined and separate pressurization andproduction wells embodying the invention.

Fig. l is a cross-sectional view of an earth formation in an oil fieldshowing a well comprising the preferred 7 modification of applicantsinvention which is used both i for pressurization and production.

. Fig. 2.is' a cross-sectional View through the same earth formation asis shown in Fig. l in an oil field showing two wells, the left well inFig. 2 being used only for production and the right well in Fig. 2 beingused only for pressurization.

Fig. 3 is a cross-sectional view of an earth formation in an. oil fieldshowing two wells, the well on the left being used only for productionand the well on the right .beingiused only for pressurization, the twowells being used in conjunction one with the other.

In the drawings, the ground level is indicated by numeral 10. Oil sandor horizon 11 has relatively im- (asphaltic or resinous) or cement whichextends from the top of the oil horizon to any desired level above theoil horizon. The pressurization seal is of such strength I as to retainwithin the too of the oil horizon any pressures which may be applied tothe horizon through the pressurization casing 16. Pressurization casing16 has 7 pressure input line 19 and valve 2% thereon, the input linebeing attached to any conventional source of gaseous pressure (notshown).

The center well in Fig. 2 illustrates a production Well 7 having borehole 21 which extendsto the vicinity of the bottom of the oil horizon.Production tubing 22 having conventional T 22 on he upper end thereofextends from the surface of the ground to the vicinity of thePressurization casing 16 extends into.

bottom of the oil horizon and has perforations 23 in the lower portionthereof. T 22a permits either flowing or pumping of the fluids whichenter tubing 22 through perforations 23. Attached to the sealed upperend of tubing 22 is fiowline 24 having valve 25 therein. Tubing 22 issealed to the well wall of the oil horizon just above the bottom of theoil horizon and above the perforations 23. This seal is accomplished byconventional packer 26. A column of sealing material 27 extends from thetop of packer 26 to a level above the top of oil horizon 11. The sealingcolumn 27 and packer 26 are sealed to the well wall with such strengthas to prevent any leakage of pressure medium along the well wall at theoperating pressures of the oil production pressurization method.

The well in Fig. 1 is employed as a combination pressure and productionwell. This well has a bore hole 28 drilled to the vicinity of the bottomof oil sand 11. Primary casing 29 extends from the surface 10 to the topof the oil horizon 11. Casing 29 is sealed to the wall of thesurrounding formations by an annular column of sealing substance 30which extends from the top of the oil horizon to a level above the topof the oil horizon. Such sealing column is of suficient strength as toprevent any leakage of pressure medium into the overlying formations atthe operating pressures of the oil pressurization process. Casing 29 hassealed bradenhead 31 with pressure fiowline 32 attached thereto havingvalve 33 therein. Pressure line 32 is attached to any. conventionalpressurization source (not shown). Production tubing 34 extends to thevicinity of the bottom of oil horizon 11 and is sealed at its upperextremity to bradenhead 31. Tubing 34 has perforations 35 at the lowerend thereof. Production flowline 36 having valve 37 is attached to thesealed head of tubing 34; Tubing 34 is sealed to the oil horizon wellwall at a level immediately above the bottom of the hole bore, oilhorizon and perforations 35. This seal is accomplished by conventionalpacker 38 which vertically seals off the annulus between the tubing 34and the well wall or hole bore 28. The seal between packer 33 and thewell wall is of such strength as to prevent by-passing under thepressures employed in the oil production method. The packer 38 is alsoof sufiicient width to readily establish suflicient sealing surface. Aindicates a first level of fluid in the annulus between tubing 34 andwell wall 2 8 in the operation of the inventive method, B indicates asucceeding operative level of fluid in the said annulus and C indicatesa further succeeding level of fluid to fluid level B in the annulus inthe operation of the inventive method. These levels will be furtherexplained in the following description of the method.

The operation of the inventive method will be described separately withrelation to the various figures. As the well at the left contains thepreferred form of apparatus and the preferred inventive method isemployed herein, the method as operated in this well will be describedfirst.

. Referring now to the well illustrated at'the left in the Figure 1, itshould be pointed out that this well, em-

ploying the apparatus shown therein, can be operated either as acombined pressurization and production well or, in conjunction withanother pressurization well such as the example shown in Fig. 3, assolely a production well. These two functions will be separatelydescribed and the operation as a combined pressurization and productionwell will be described first.

With'the well completedas set forth in the previous 7 description and asshown in Figure 1, a petroleum. crude fluid of equal or higher viscositythan the liquid hydrocarbons contained in the natural oil reservoir willpreferably be poured into the annulus between the tubing 34 and wellwall 28 so that the upper surface of said fluid will stand in theannulus to a level above the top of the oil horizon such as thatindicated at level A. In selecting the fluid just mentioned, it isrecommendedthat ensures the fluid beslightly higher in viscosityand-slightly lower in gravity than-the fluid resident in the earth oilreservoir into which the well described is drilled. A sufliciently-weathered sample of oil from the same reservoir will suf- -fice for theforegoing stated purpose.

It is contemplated that many other fluids, including but not limited towater and oil of various viscosit-ies and gravities, may be em- 'ployedbut the foregoing fluid is preferred.

Having filled the annulus to the level designated as A,

- pressure is then applied through flowline 32 to casing 29 isuflioiently high degree to force the fluid placed in the annulus toenter the oil reservoir at points above the pressure tight seal- 38. Asthis fluid is forced into-the reservoir, the upper-level of the fluid inthe annulus will gradually drop until it comes to the 'level designatedas B. As

. the top of the fluid column passes the casing shoe of casing 29 in theoil reservoir, the compressed gas or air being usedv to force the fluidcolumn into the oil reservoir will immediately find a means of escapedirectly into the reservoir. This escape will, of course, retard thedownward movement of the upper surface face of the fluid column. The oilhorizon is naturally more permeable to the gaseous pressure medium thanto-the fluid in the fluid column.

' While the downward movement of the upper face of the fluid column willbe retarded, it will not stop until enoughof the sand face of the holebore has been exposed to take It should be noted that as thepressurization This segregation results in the formation of apressurization mediumfluid or gasoil interface within the horizon,which, as the gas cap expands and increases in volume, moves graduallydownwardy through the horizon. While the pressurization is going on atthe top of the formation, oil is withdrawn from the lower portion of theformation through vperforations 35 and tubing 34 below packer 38. As thepressurization continues, the interface constantly, though gradually,moves downwardly through the horizon. The

level of the top of the fluid column in the annulus will coincideessentially at all times with the level of this gas 1 oilinterfacewithin the' horizon. -Thus, it should be noted that, effectively, acomplete seal is created within the well bore from the top of theannulus column of fluid to the bottom of packer 38 during thepressurization process.

As the gas-oil interface migrates gradually downwardly in the horizon,so also will the top surface of the annulus column of fluid migratedownwardly. I This progression is indicated in the drawings by level Cand is followed as above stated until the gas-oil interface in thereservoir reaches a level adjacent the bottom of packer 38. When thegas-oil interface in the reservoir has moved toth-is point parallel tothe base of the. sealing device 33 and the topmost portions of theperforations 3S,

thiswellwillhave lost its purpose and function as an oil producer butmay still be utilized as a pressure in- .earth center than is the casein this particular well. Therefore, production would continue from thoseWells which are located at the lowest point or points in the reservoir.

Should it be desired to operate a well similar to the well in the Figurel'as a production unit only, such well may be employed-in conjunctionwith a pressurization well such as is shown in the Figure 3. To thispurpose, the annulus between the tubing 34 and the well wall is againfilled with fluid, as previously described, in sufiicient volume so thattheupper surface ofsaid fluid will standin the annulus the'fluid columnin the annulus.

' to a levelabove-the top of the oil reservoir such as that indicated aslevel-A.

Pressure in the form of gas or air is then applied to the top portion ofthe oil horizon through the pressurization well casing 16 throughpressure input line 19. 'Again, a gas cap and gas oil or pressuremeclium-sand fluid interface are formed as previously described as thepressurization continues. zation process aflects the sand fluids, oilmay be produced -from tubing 34 through perforations 35. Valve 33 is Asthe pressurikept closed during the pressurization process. When the gascap reaches the bore hole 28 of the production well, the gas immediatelyrises through the fluid to the volume above the. level A and exertspressure downwardly-on The top of the fluid column is then graduallyforced, during the pressurization rocess, downwardly until itcoincideswith the level of the gas-oil interface in the oil horizon. The level ofthe top of the fluid column then migrates gradually downwardly as thegas-oil interface migrates downwardly, as previously 7 unit.

described in the description of the operation of the well ,as a combinedpressurization and production well. This downward.progression continuesuntil the gas-oil inter- ;face again passes below the lower edge ofpacker 38 when,

again, the production well becomes useless as a production Should therebe any leakage pas packer 38 of fluid during pressurization, more may beadded thereabove.

The method as employed in a combination pressurization and productionwell as in Fig. 1 may be summarized as comprising the following steps:(1) drilling the bore hole of an oil well to the vicinity ofthe bottomof an oil horizon, (2) running a primary casing having a pressureflowline thereon to the top of the oil horizon,

(3) sealing said primary casing to the surrounding formationsfrom thetop of the oil horizon to a level above the top of the oil horizon toeffect a pressure-tight seal above said horizon, (4) running a tubingperforated at its lower end and sealed to the primary casing above thesurface to .the vicinity of the bottom of the hole bore and oil horizon,(5) sealing said tubing to the well wall in the vicinity of the bottomof the oil horizon, (6) filling the annulus between the well wall andthe tubing with fluid to a level above the top of the oil horizon, (7)applying pressure to the top of the fluid column in the annulus wherebythe top of the column is forced below the top of the oil horizon, (8)continuously applying pressure to the topof the column and well boreface, and (9) producing oil through the tubing below the tubing-wellwall seal. Oil may bepumped from the tubing should the oil sand or oilhorizon pressure be insuflicient to flow the oil to the surface.

The method as applied in separate pressurization and production wellshaving apparatus as shown in Figure 3 may be summarized in the followingsteps: (1) drilling the bore hole of an oil well to the vicinity of thebottom of an oil horizon, (2) running a primary casing to the top of theoil horizon, (3) sealing said primary casing to the surroundingformations from the top of the oil horizons to a level above the top ofthe oil horizons -to efiect a pressure-tight seal above said horizon,(4) running a tubing perforated at its lower end andsealed to theprimary casing above the surface to the vicinity of the bottom of thehole bore, (5) sealing said tubing to the well wall in the vicinity ofthe bottom of the oil horizon employing a pressure-tight packer, (6)filling the annulus between the Well wall and tubing with fluid to alevel above the top of the oil horizon, (7) drilling a pressurizationwell into the top of the oil horizon, v(8) running a pressurizationcasing having a pressurization flowline thereto into the top of the oilhorizon, (9) sealing the pressurization casing from the top of the oilhorizon to a level above the top of the oil horizon so as to eflect apressure-tight seal above said oil horizon, (l0) applying gaseouspressure to the top of the oil horizon through the pressurization casingwhereby an expanding gas cap is formed within said horizon and (11)producbelow the tubing-well wall seal. from the tubing should theformation pressure under the enemas ingoil through the tubing belowthetubing-Well wall 1 sea]. In this instance also, oil may be pumpedfrom the tubing if the horizon pressure is insufficient to flow the-oilto the surface. tion and production wells may be employed if desired.

A plurality of both pressurizae method, as shown in this modification,may be described in the following steps: (1) drilling the bore hole ofan oil well to the vicinity of the bottom of an oil horizon, (2) runninga production tubing having perforations in the lower end thereof to thevicinity of the bottom of the hole bore, (3) sealing the productiontubing to the well wall in the vicinity of the bottom of the oil horizonwith a pressure-tight packer, (4) filling the annulus between the wellwall and the tubing above the upper surface of said packer with a columnof sealing material or cement to a level above the top of the oilhorizon so as to form a pressure-tight seal between the sealing columnand the well wall from a level above the top of the oil horizon to thebottom surface of the packer, (5) applying gaseous pressure to the topportion of the oil horizon through a separate pressurization wellwhereby a gas cap is formed in the horizon and (6) producing oil fromthe tubing Oil may be pumped pressurization process be insufficient toflow the oil to the surface. As the formation is pressurized from anexternal pressurization well, such as either the wells on the left orthe right in the single figure, a gas-oil interface is formed within thehorizon, as previously described,

' which migrates gradually downwardly in the formation as thepressurization process continues.

When the gas cap reaches the well wall of the production well, due tothe complete seal between the well wall and sealing column, there is novertical leakage upwardly or downwardly along the face of the hole bore.Therefore, there is no intercommunication between the pressurizationzone in the upper portion of the formation and the production zones inthe lower portion of the formation until the gasoil interface passes thelower edge of the packer.

I seals in bothpressure and production wells must be of sufficientstrength to secure whatever pressures are employed in driving the fluidand gaseous hydrocarbons downwardly through the sand body and must offerno means of escape for these pressures except at the points designatedat the base of the oil sand. Additionally, it is very important that thecement or sealing material in the annular sealing column of the centerwell bond with the oil saturated wall of the oil horizon and thusprevent any marginal migration of the pressure agent or sand fluiddownward between it and the oil sand once the pressurization agent comesin contact, as it must, with the sealed well bore.

7 7 It should be pointed out that this method will successfully produceoil from the black sand portion of oil horizons possessing such.Previous methods have invariably completed above this level due to itsimpermeability and lack of productivity. Therefore, in the drawings, theproduction wells have been shown completed through this layer.

When 7 this latter event occurs the production well becomes use- Thisapplication is not based on theory but is supported by actualperformance, this date, in actual wells now producing oil employing theinventive method and apparatus. The wells are completed exactly as shownin the single figure in a section of an oil field in eastern Kansas.

From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forthtogether with other advantages which are obvious and which are inherentto the method.

it will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense Having thusdescribed my invention, I claim:

1. A method of producing oil from oil wells comprising the steps ofdrilling the borehole of an oil well to the vicinity of the bottom of anoil horizon, running a primary casing having a pressure flow linethereon to the top of the 'oil horizon, sealing said primary casing tothe surrounding formations from the top of the oil horizon to a levelabove said oil horizon with a seal of such strength and extent as toconfine within the oil formation such pressures as may be applied to thetop of the horizon in the oil production method, running'a tubing havinginlet means at the lower end thereof sealed to the primary casing abovethe surface of the ground to the vicinity'of the bottom of the holebore, sealing said tubing to the well wall in the vicinity 'of and abovethe bottom of the oil horizon and above the lower end of the tubing witha seal of such strength and extent as to prevent leakage along the facethereof under such pressures as may be employed in the productionmethod, filling the annulus between the well wall and the tubing abovethe seal with a liquid which will penetrate the horizon on applicationof the operating pressures of the method thereto to a level above thetop of the oil horizon, applying gaseous pressure to the top of theliquid column in the annulus through said pressure flow line whereby thetop of the column is forced below the top of the oil horizon and atleast some of the liquid is forced out into the oil horizon, continuingto apply gaseous pressure to the top of the liquid column and oilhorizon through said pressure flow line whereby to force thepressurization medium into the upper portion of the oil horizon and movethe oil therein downwardly in the horizon into the inlet means of thetubing, and producing oil through the tubing below the tubing-well wallseal.

2. A method as in claim 1 wherein oil is pumped from the tubing.

3. A method of producing oil from oil wells comprising the steps ofdrilling the borehole of a production oil well to the vicinity of thebottom of an oil horizon, running a primary casing sealed at its upperend to the top of the oil horizon, sealing said primary casing to thesurrounding formations from the top of the oil horizon to a level abovethe top of the oil horizon with a seal of such strength and extent as toconfine within the oil formation such pressures as may be applied to thetop of the oil horizon during the operation of the method, running atubing having inlet means at the lower end thereof and sealed to thecasing above the surface, to the vicinity of the bottom of the holebore, sealing said tubing to the well wall in the vicinity of and abovethe bottom of the oil horizon and lower end of the tubing with a seal ofsuch strength and extent as to prevent leakage across the face thereofat the pressures employed in the production method, filling the annulusbetween the well wall and the tubing above the. seal with a liquid whichwill penetrate the oil horizon on application of the operating pressuresof the method thereto to a level above the top of the oil horizon,drilling a separate pressurization well into the top of the oil horizon,running a pressurization casing having a pressurization flow linethereto at least to the top of the oil horizon, sealing saidpressurization casing from the top of the oil horizon to a level abovethe top of the oil horizon with a seal of such strength and extent as toconfine within the oil formation such pressures as may be encounteredduring the operation of the production method, applying gaseous pressureto the top of the oil horizon through the pressurization casing wherebyan expanding gas cap is formed in the top of the oil horizon which uponmigration to the borehole of the production well forces the top of theliquid column therein below the top of the oil horizon and at least someof the liquid in the annulus into the oil horizon, continuing to applygaseous pressure to the top of the oil horizon through thepressurization casing whereby to force the pressurization medium intothe upper portion of the oil horizon and move the oil therein downwardlyin the horizon into the inlet means of the tubing, and producing oilfrom the tubing below the tubing-well wall seal.

4. A method as in claim 3 wherein oil is pumped from the tubing.

5. A method as in claim 3 wherein gaseous pressure is applied to the topof the oil horizon from a plurality of pressurization wells.

6. A method of producing oil from oil wells comprising the steps ofdrilling the borehole of a production oil well to the vicinity of thebottom of an oil horizon, running a primary casing to the top of the oilhorizon, sealing said primary casing to the surrounding formations fromthe top of the oil horizon to a level above the top of the oil horizonwith a seal of such strength and extent as to contain within the horizonany pressures which may be applied thereto in the operation of theproduction method, running a tubing sealed to the casing above thesurface and having inlet means in its lower end to the vicinity of thebottom of the hole bore, sealing said tubing to the well wall in thevicinity of and above the bottom of the oil horizon and tubing lower endwith a seal of such strength and extent as to prevent pressure leakageacross its face under the pressures applied to the oil horizon duringthe operation of the production method, filling the annulus between thewell Wall and the tubing above the seal with a liquid which willpenetrate the oil horizon on application of the operating pressures ofthe method thereto to a level above the top of the oil horizon, applyinggaseous pressure to the top of the oil horizon whereby to force the topof the liquid column in the production well borehole below the top ofthe oil horizon and at least some of the liquid in the annulus into theoil horizon, continuing to apply gaseous pressure to the top of the oilhorizon to force the pressurization medium into the upper portion of theoil horizon and move the oil therein downwardly in the horizon into theinlet means of the tubing, and producing oil through the tubing belowthe tubing-well wall seal.

7. A method as in claim 6 wherein the liquid employed to fill theannulus between the well wall and the tubing is of a viscosity andgravity essentially the same as the liquid already resident in the oilformation and will penetrate the oil horizon on application of theoperating pressures of the method thereto.

8. A method as in claim 6 wherein the liquid-employed to fill theannulus between the well wall and the tubing is greater in viscosity andlower in gravity than the liquid resident in the oil horizon and willpenetrate the oil horizon on application of the operating pressures ofthe method thereto.

9. A method as in claim 6 wherein the liquid employed to fill theannulus between the well wall and the tubing is a hydrocarbon which willpenetrate the oil horizon on application of the operating pressures ofthe method thereto.

References Cited in the file of this patent UNITED STATES PATENTS1,252,557 Dunn Jan. 8, 1918 1,457,479 Wolcott June 5, 1923 1,816,260 LeeJuly 28, 1931 2,044,657 Young June 16, 1936 2,377,529 Stephenson June 5,1945 2,593,497 Spearow Apr. 22, 1952 2,725,106 Spearow Nov. 29, 1955

